The Mk3 is for you if you wear a Half Height, Shorty, or Bell Cycle style helmet. It will also fit MOTO helmets, but only those without a visor (the helmet cover is best trapped under the detachable peak). The Mk3 will fit a helmet with an external circumference of 31 to 33 inches (80cm to 84cm) and it does not cover the "cheek" areas of a "Jet" style helmet.